What voltage are 3D printer fans? 12 V, 24 V and mixing them

A 3D printer fan runs at its header’s voltage, usually the printer’s DC supply. That is 24 V on many current printers, including the Creality Ender 3, and 12 V on older machines like Prusa’s MK2. Some boards feed fans at 5 V. Buy the fan to match the header.

What voltage are 3D printer fans?

3D printer fans run at whatever voltage the board puts on the fan header, usually the printer’s supply voltage. On a 24 V printer such as the Creality Ender 3, that means 24 V fans. Prusa’s MK2 and MK2.5 run on 12 V. Some boards let you set each header to 5 V, 12 V or 24 V.

Noctua names the Creality Ender 3 and the Anycubic Mega as 24 V printers that use 40 mm or 60 mm fans.

Printer	Supply	Fan voltage
Creality Ender 3	24 V	24 V
Anycubic Mega	24 V	24 V
Prusa MK2, MK2S, MK2.5, MK2.5S	12 V	12 V

Creality’s 4010 replacement fan kit is a 24 V part, listed for the Ender 3 and CR-10S among others. Prusa’s MK2.5S+ upgrade guide warns that the MK2 family runs on 12 V, so don’t buy parts that need 24 V. That guide’s hotend fan is a 5 V part, and Prusa notes it needs an adapter cable on the MK2.5 board.

Boards with selectable fan voltage

Some mainboards set the voltage for each fan header with jumpers:

• BIGTREETECH Octopus: six fan outputs with pulse-width modulation (PWM) speed control and two always-on outputs. A jumper sets each one to the input voltage (24 V on a 24 V printer), 12 V or 5 V. The Octopus wiki warns that a jumper placed any other way than shown will likely damage the board.
• Duet 3 Mainboard 6HC: jumpers set each bank of three fan outputs to the input voltage or 12 V. The 12 V option comes from an onboard regulator rated 800 mA in total, per Duet’s fan documentation.

On these boards the jumper, not the supply, sets the header voltage. Check it before you plug in a new fan.

How to check your fan and header voltage

1. Read the fan’s label. The sticker on the hub gives the rated voltage and current, for example “DC 24V 0.11A”.
2. Check the board. The printer’s spec sheet or the board’s manual gives the supply voltage. On a board with jumpers, find the jumper next to that header.
3. Measure the header. Set a multimeter to DC volts and switch the printer on. Turn the part cooling fan to 100 percent with M106 S255 (Marlin and Klipper); a hotend fan usually switches on by itself once the hotend heats. Probe across the header’s two pins, keeping the probes off neighboring pins.

Don’t measure from one pin to the frame. Duet’s documentation explains that its controlled fan headers switch the fan’s negative wire. On a board like that, the + pin measured to ground shows the full supply voltage even with the fan at 0 percent.

Turn the printer off before you unplug or swap a fan.

Can you run a 12 V fan on a 24 V 3D printer?

Not directly. A 12 V fan on a 24 V header gets twice its rated voltage and will be damaged, as Noctua warns. Delta’s 12 V 5015-size blower is rated up to 13.8 V. Fit a 24 V fan of the same size, or feed the 12 V fan through a 24-to-12 V step-down converter.

Noctua’s FAQ allows it only after the 24 V is converted down to 12 V. Three fixes, from simplest to least reliable:

1. Buy the 24 V version of the same fan. This is the usual fix. The section below covers what to match.
2. Add a step-down (buck) converter. Wire it from the 24 V supply to a 12 V output for the fan. Duet’s documentation shows this wiring for 12 V fans on a 24 V board, with the fan’s negative wire still on the controlled header so PWM keeps working. Noctua sells the NA-VC1, a 24-to-12 V converter for its 12 V fans on 3D printers. It supplies up to 9 W in total and has a resettable fuse.
3. Wire two identical 12 V fans in series. Each fan gets about 12 V, but only if the two match. This suits only plain 2-wire fans running at full speed. One Duet forum user found that at low PWM settings only one fan of a series pair would spin. Skip it for 3- and 4-wire fans: their speed-sense and PWM wires work against the fan’s own ground wire, and in a series pair one fan’s ground sits at 12 V.

What to match when buying a 24 V 3D printer fan

• Size and type. A 4010 is a 40 x 40 x 10 mm fan. Swap a blower for a blower and an axial fan for an axial fan, since the shroud or duct is shaped for one.
• Voltage. 24 V, or whatever your header measured.
• Current. Inside the header’s limit, counting any other fan on the same output.
• Wires. A 2-wire fan has power and ground only. A 3-wire fan adds a tachometer (speed-sense) wire, and a 4-wire fan adds a PWM input, as Duet’s wiring table shows. Match what your board and firmware use.

What happens if you put a 24 V fan on 12 V?

It runs slowly or doesn’t start. Delta’s 24 V 5015-size blower is rated for 14.0 to 27.6 V, so 12 V is below its operating range and Delta doesn’t promise it will spin there. Low voltage won’t burn the fan out. A slow fan still won’t move its rated airflow, which matters most for the hotend.

Do 24 V and 12 V fans use the same power?

Yes, nearly. A 24 V fan draws about half the current of its 12 V version for the same power. Delta makes the same 51 x 51 x 15 mm blower in 12 V and 24 V:

Delta blower	Rated voltage	Operating range	Current	Power
BFB0512HH	12 V	10.0 to 13.8 V	0.21 A	2.52 W
BFB0524HH	24 V	14.0 to 27.6 V	0.11 A	2.64 W

Both spin at 6,500 rpm and move 4.59 cubic feet per minute (CFM) of air. The 24 V version does it on half the current.

How much current can a fan header supply?

Check the fan’s current against the header’s limit, especially when two fans share an output. Duet rates each fan connector on its Duet 2 and Duet 3 boards for 2 A. The 12 V regulator on a Duet 3 6HC is limited to 800 mA in total. Your board’s manual gives its own limits.

current = fan watts ÷ fan volts
2.64 W ÷ 24 V = 0.11 A per 24 V blower

two 12 V blowers on the 6HC's 12 V regulator:
2 × 0.21 A = 0.42 A, inside an 800 mA limit

Fans draw a few watts each, a small part of a printer’s DC load. Add them to the bed, hotend and motors in the power supply calculator when you size a new 12 V or 24 V supply. The guide to what voltage a 3D printer uses covers the mains side and the DC rail.